Additives for use in extreme pressure gear oils



Patented May 26, 1953 ADDITIVES FOR USE IN EXTREME PRESSURE GEAR OILS Fred B. Fischl, Rahway, and Max W. Hill, Somerville, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application March 1, 1951, Serial No. 213,455

The present invention relates to additives for use in extreme pressure gear oils and the like. It relates particularly to phosphorus and sulfur containing compositions designed to enhance the load carrying capacity of lubricating oils, greases, and the like, employed where unit loads are exceptionally high as for example in automotive differential units, hypoid gearing and the like. The invention pertains also to an improved method for preparing such additives and to lubricants containing them in appropriate proportions.

Numerous suggestions have been made in the prior art for the treatment of various materials with phosphorus, sulfur, and phosphorus sulfides. The prior art recognizes the fact that lubricants containing phosphorus and sulfur, among other things, are capable of carrying higher unit loads Without failure of the lubricating film than are lubricants which do not contain these elements. It has also been suggested that fatty oils, mineral base oils and various other organic materials, appropriately treated with phosphorus, sulfur, or phosphorus sulfides have utility as extreme pressure lubricant additives.

It has been suggested further in the prior art that certain hydrocarbon oils, such as the bright stock lubricating oil may be treated with phosphorus sulfide and the present invention is related in general subject matter. According to the present invention, bright stocks and the related mineral lubricating oil base stocks, may be treated at relatively high temperatures with various phosphorus sulfides, especially Pass, although P433 and others may also be used. Treatment should be continued long enough to add substantial phosphorus. The resulting reaction products are further treated with organic materials which stabilize the phosphorus sulfide treated oil, reducing or eliminating its corrosive- 13 Claims. (Cl. 252-465) ness toward copper, for example, substantially eliminating objectionable odors and tendencies to evolve I-IzS and related sulfurous gases and completely removing any sludge forming tendencies.

According to the present invention, a mineral lubricating oil base stock of about 50 to 250, S. S. U. viscosity at 210 F., or of higher viscosity, is treated with a substantial proportion of a phosphorus sulfide at an elevated temperature.

The proportions of the phosphorus sulfide may vary from as little as 5 to as much as 25%, the

preferred range being around 1 0 to 20% of the phosphorus sulfide, based on the weight of the oil. The treating temperature employed is in the range of 375 to 475 F., preferably in the range of 400 to 430 F. The oil obviously must be of such type, including viscosity and boiling: point, that it remains stable during the treatment. The time of treatment may vary somewhat, from as little as l-hour to as much as 20 hours or more, but it is preferably continued for several hours, for example 10 hours or so and until the oil has a phosphorus content of 3% or more by weight and a sulfur content of- 5% or more by weight. The phosphorus content may go as high as 5 or 6% and the sulfurv content as high as 10 to 12%, but treatment should not be extended to the point that the material becomes insoluble in the gear oil base stock where it is to be used. Ordinarily the upper limit is about 5 to 6% for the phosphorus content and about 9 to 11% for sulfur. This phosphorus content, in particular is higher than in most prior art practices.

A particularly suitable lubricating oil base stock is a deasphalted and dewaxed clay treated Panhandle bright stock having a viscosity around 1'70 S. S. U. at 210 F. This particular oil appears to contain a substantial proportion of alkyl substituted aromatics. These apparently, are more reactive with the phosphorus sulfide than the paraflins and they make it'possible 'to obtain a substantially higher phosphorus content than can be secured with the essentially paraflinic lubricating oils. In any case, however, the oils selected should be treated at high temperatures for extended periods "so as to obtain a high phosphorus content. The phosphorus content desired is several times, and may be as much as 10 to 15 times, as high as in common prior art additives of this type.

The odor of the bright stock, treated in the manner described, is highly objectionable because there is usually a spontaneous evolution of H28 gas, showing afairly high degree of instability in the reaction product. In order to eliminate this instability, which is evidenced also in a high degree of corrosivity toward copper,

the reaction product of the oil and phosphorus sulfide is further treated.

The further treatment which stabilizes the phosphorus and sulfur-containing oil consists in heating the treated oil with proportions, preferably from about 5 to about 30% of its weight of a sulfurized fatty oil or a lower alcohol ester thereof. The unsaturated fatty materials are preferred. The sulfurized fatty oils to be used, such as sulfurized sperm oil, for example, having a sulfur content of 5 to 25%, preferably 6 to 20% are easily prepared by heating fatty oils with sulfur at an elevated temperature such as 300 F.

Th sulfurized fatty oil is mixed and heated with the phosphorus sulfide treated lubricating oil at a temperature of about 250 to 450 F., preferably 300 to 400 F., for a period sufficiently long to substantially reduce the evolution of HzS and/or the corrosivity toward copper. The time of reaction may be from 1 to 15 hours, 2 to 8 hours being generally suificient.

The phosphorus sulfide treated oil, stabilized by the further treatment described above is a potent extreme pressure additive which is substantially free from the objectionable odor of sulfur and sulfur-containing volatile materials and is not corrosive to copper at normal operating temperatures. The finished material, however,

contains a relatively very large proportion of phosphorus, e. g. 2% or more and at least 5% sulfur. These elements, as incorporated by the procedure of the present invention, are sufficiently active to give the necessary film protection under conditions of extreme pressure. When the ordinary lubricating film fails, the instantaneoustemperature rise at the point of contact causes formation of a phosphide or sulfide film on the metal surfaces to preserve them from mutual injury due to Welding and/or abrasion.

The invention will be further illustrated by reference to specific examples.

EXAMPLE I Adeasphalteddewaxed clay treated Panhandle bright stock of 170 S. S. U. viscosity at 210 F. was treated in a nitrogen atmosphere with 17.5% by weight, based on the oil, of PzSs for 10 hours at a temperature of 400 F. Thereafter the product was filtered and reacted with 20% by weight of; sulfurized sperm oil containing 12% sulfur. This reaction was carried out at a temperature of 250 F. for ll-hours, followed by heating to 400 F. for another hour; the ingredients being constantly stirred.

The following data show the performance of these materials all of them being used in proportionsof 10% in a standard gear oil base lubricant.

Table I after the sulfurized fatty oil treatment. It contained 0.28% phosphorus, had a viscosity of 1182 S. S. U. at 100 F. and 97.7 at 210 F., a viscosity index of 97, a flash point of 480 F., and a pour point of +10 F.

Table IA PERFORMANCE OF GEAR LUBRICANTS FORMU- LATED WITH P S TREATED BRIGHT STOCK TYPE EXTREME PRESSURE ADDITIVES Composition of additive: I

P285 treated bright stoclL Sulfurized sperm oil (12% S.) 20

Analysis of finished additive, weight per cent:

1 M Military Establishment Specification Taste It will be noted from the foregoing that gear lubricants formulated with the products treated with sulfurized sperm oil meet the requirements of the Military Establishment Specification MIL-L-2105 both with regard to full scale. gear performance and also regarding thermal stability..

tions in lubricating oils, depending upon the specific application. In the lubrication of automotive hypoid gears, a concentration of. 5 to. 20%,

- preferably 8 to 10%, is generally required for satisfactory operation.

- It is generally not recommended to formulate gear lubricants with P285 treated bright stock without further reacting it with unsaturated and/or sulfurized materials because such a lubricant although possessing satisfactory gear performance is thermally unstable, precipitating insoluble sludge on storage, and, furthermore, has a quite objectionable odor.

Stability of the lubricant in storage, as well as under actual operating conditions, is of considerable importance to insure satisfactory lubrication over long periods of time. In order to PE RFORMANOE OF EXTREME PRESSURE GEAR OILS [10% by weight additive blends in SAE base stock] The oil blend of Example I (10% in SAE 90 oil) showed a sulfur, content of 1.34% by weight,

achieve satisfactory thermal stability, the phospho-sulfurized lubricating oil must be further reacted with the sulfurized fatty materials at elevated temperatures as described above. It appears that the reaction temperature of the treating step has a significant effect on the stability of the composition.

In lieu of sulfurized sperm oil, other sulfurized fatty oils and related esters such as hydroabietates, abietates, methyl or ethyl esters of lard oil, tall oil esters, coconut oil esters, etc., may be used. These should be sulfurized to a sulfur content of 5 to 25% or more, preferably at least 6% for severe extreme pressure service.

It will be understood that other usual additives may be employed along with these extreme pressure additives such as thickeners, viscosity index improvers, oxidation inhibitors, metal deactivators, pour point depressants, soaps and other thickeners and the like as is well understood by those skilled in the art.

What is claimed is:

1. An extreme pressure additive composition for lubricants, comprising a major proportion of a mineral lubricating oil base stock treated with 5 to 25% of its weight of a phosphorus sulfide at a temperature of 325 to 475 F. for 1 to hours, said product being further treated with about 5 to 30% by weight of a sulfurized fatty material at about 250-450 F. for about 1-15 hours to stabilize it against evolution of H28 gas.

2'. Composition according to claim 1 wherein the further treatment is with 5 to 30% of the weight of the treated mineral oil with :a sulfurized unsaturated fatty ester of 5 to sulfur content having a higher fatty acid radical, for 2 to 10 hours at 250 to 425 F.

3. An extreme pressure additive composition for lubricants, consisting essentially of a mineral lubricating 011 base stock of 50 to 250 S. S. U. viscosity at 210 F., treated with a phosphorus sulfide at a temperature within the range of 375 to 475 F. for a period of time of about 1-20 hours to incorporate about 3-6% by weight of phosphorus and about 5-12% of sulfur into the oil, said treated oil being stabilized by further treatment with 5 to of its weight of a material selected from the class which consists of sulfurized fatty oils and their lower alcohol esters at a temperature in the range 250 to 450 F., for 2 to 10 hours.

4. Composition according to claim 1 wherein said phosphorus sulfide is primarily P255.

5. The process which comprises treating a mineral lubricating oil base stock of viscosity between 50 and 250 S. S. U. at 210 F., with 5 to 25% of its weight of P285 at a temperature within the range of 375 to 475 E, for 1 to 20 hours to incorporate a phosphorus content of about 3-6% by weight and thereafter heating the product with 5 to 30% of sulfurized fatty oil containing 6 to 20% of sulfur for a period of 2 to 8 hours and at a temperature within the range of 300 to 6. The process which comprises first treating a mineral lubricating oil base stock of viscosity between about 50 and 250 S. S. U. at 210 F. with 5 to 25% of its weight of a phosphorus sulfide at a temperature within the range of 375 to 450 F. for a period of l to 20 hours, and thereafter reacting the product at a temperature within the range of 250 to 450 F., with 5 to 30% of its weight of a liquid stabilizer selected from the group which consists of the sulfurized fatty oils and sulfurized lower alcohol esters thereof until the product is substantially non-corrosive toward copper at temperatures below about 200 F.

7. Process according to claim 6 wherein said phosphorus sulfide is essentially Pass.

8. Process according to claim 6 wherein said stabilizer is sulfurized sperm oil of 5 to 20% sulfur content.

9. The process which comprises reacting a mineral lubricating oil base stock with about 15 to 20% by weight of P285 at a temperature of about 400 F. for about 8 to 12 hours, filtering the product, and treating the filtered product with about 15 to 25% of its weight of sulfurized sperm oil of 10 to 15% sulfur content at about 250 F, to 450 F. for about 3 to 5 hours, to stabilize it against evolution of sulfur containing gases and/or excessive corrosivity toward copper.

10. The process which comprises reacting a mineral lubricating oil base stock with about 15 to 20% of its Weight of P285 at a temperaturev of about 400 F. to 430 F., for about 8 to 12 hours, filtering the product, and treating the filtered product with about 15 to 25 of sulfurized sperm oil of about 12% sulfur content for 3 to 5 hours at about 250 F. to 450 F., to stabilize it against decomposition on storage when blended into a base stock, and against evolution of sulfur containing gases and excessive corrosivity towards copper.

11. The product of the process of claim 10.

12. A lubricating composition comprising a major proportion of a viscous lubricating oil and 5 to 20% by weight of the composition of claim 1.

13. A lubricating composition comprising a major proportion of a viscous lubricating oil and about 5 to 20% by weight of the composition of claim 3.

FRED B. FISCHL. MAX W. HILL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,316,086 McLaren Apr. 6, 1943 2,396,345 Rogers et al. Mar. 14, 1946 2,450,405 Berger et al. Oct. 5, 1948 2,560,547 Bartleson July 17, 1951 FOREIGN PATENTS Number Country Date 510,926 Great Britain Aug. 10, 1939 

3. AN EXTREME PRESSURE ADDITIVE COMPOSTION FOR LUBRICANTS, CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL BASE STOCK OF 50 TO 250 S. S. U. VISCOSITY AT 210* F., TREATED WITH A PHOSPHORUS SULFIDE AT A TEMPERATURE WITHIN THE RANGE OF 375* TO 475 F. FOR A PERIOD OF TIME OF ABOUT 1-20 HOURS TO INCORPORATE ABOUT 3-6% BY WEIGHT OF PHOSPHOROUS AND ABOUT 5-12% OF SULFUR INTO THE OIL, SAID TREATED OIL BEING STABILIZED BY FURTHER TREATMENT WITH 5 TO 30% OF ITS WEIGHT OF A MATERIAL SELECTED FROM THE CLASS WHICH CONSISTS OF SULFURIZED FATTY OILS AND THEIR LOWER ALCOHOL ESTERS AT A TEMPERATURE IN THE RANGE 250 TO 450* F., FOR 2 TO 10 HOURS. 